Receptor-site-directed agents which are capable of alkylating analgesic receptors will be synthesized and tested in an effort to discover compounds which will be useful as pharmacologic probes to investigate narcotic receptors. The design rationale consists of modifying compounds known to form reversible complexes with narcotic receptors by attachment of suitable reactive functional groups which possess the potential for covalent bond formation with a proximal nucleophilic group on the receptor. The molecular appendage containing the reactive function will be varied in order to obtain a compound with optimal alkylating capacity. Pharmacologic evaluation will include testing for analgesic activity, narcotic antagonist activity, and protection experiments to determine selectivity of action.